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https://github.com/LadybirdBrowser/ladybird
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1931636ac3
When the middle mouse button is pressed, we can now scroll the pressed container while moving the mouse around. We paint an indicator at the pressed origin (as an overlay), as the scroll speed will depend upon the distance between the moved mouse and that origin.
98 lines
3.3 KiB
C++
98 lines
3.3 KiB
C++
/*
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* Copyright (c) 2026, Tim Flynn <trflynn89@ladybird.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Math.h>
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#include <LibWeb/DOM/Document.h>
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#include <LibWeb/DOM/Element.h>
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#include <LibWeb/Page/AutoScrollHandler.h>
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#include <LibWeb/Page/MiddleButtonScrollHandler.h>
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#include <LibWeb/Painting/Paintable.h>
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#include <LibWeb/Painting/PaintableBox.h>
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#include <LibWeb/Painting/ViewportPaintable.h>
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namespace Web {
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static constexpr CSSPixels DEAD_ZONE_RADIUS { 15 };
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static constexpr double SPEED_FACTOR = 5.0;
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static constexpr double MAX_SPEED_PER_SECOND = 5000.0;
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static constexpr double SCROLL_INTERVAL_MS = 16.0;
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MiddleButtonScrollHandler::MiddleButtonScrollHandler(DOM::Element& container, CSSPixelPoint origin)
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: m_container_element(container)
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, m_origin(origin)
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, m_mouse_position(origin)
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{
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if (auto* paintable = m_container_element->document().paintable())
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paintable->set_needs_repaint();
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}
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MiddleButtonScrollHandler::~MiddleButtonScrollHandler()
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{
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if (auto* paintable = m_container_element->document().paintable())
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paintable->set_needs_repaint();
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}
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void MiddleButtonScrollHandler::visit_edges(JS::Cell::Visitor& visitor) const
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{
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visitor.visit(m_container_element);
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}
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GC::Ptr<DOM::Element> MiddleButtonScrollHandler::find_scrollable_ancestor(DOM::Document& document, Painting::Paintable& paintable)
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{
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// AutoScrollHandler::find_scrollable_ancestor begins with the paintable's containing block. For middle mouse
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// scrolling, we want to include the paintable itself. This allows clicking in dead space to being scrolling.
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if (auto* paintable_box = as_if<Painting::PaintableBox>(paintable); paintable_box && paintable_box->could_be_scrolled_by_wheel_event()) {
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if (auto* element = as_if<DOM::Element>(paintable_box->dom_node().ptr()))
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return element;
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}
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if (auto container = AutoScrollHandler::find_scrollable_ancestor(paintable))
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return container;
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if (auto scrolling_element = document.scrolling_element())
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return const_cast<DOM::Element*>(scrolling_element.ptr());
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return {};
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}
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void MiddleButtonScrollHandler::update_mouse_position(CSSPixelPoint position)
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{
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m_mouse_position = position;
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m_mouse_has_moved = true;
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}
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void MiddleButtonScrollHandler::perform_tick()
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{
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auto distance_x = (m_mouse_position.x() - m_origin.x()).to_double();
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auto distance_y = (m_mouse_position.y() - m_origin.y()).to_double();
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if (auto distance = AK::hypot(distance_x, distance_y); distance < DEAD_ZONE_RADIUS.to_double())
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return;
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m_container_element->document().update_layout(DOM::UpdateLayoutReason::AutoScrollSelection);
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auto paintable_box = AutoScrollHandler::auto_scroll_paintable(m_container_element);
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if (!paintable_box)
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return;
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auto speed_x = clamp(distance_x * SPEED_FACTOR, -MAX_SPEED_PER_SECOND, MAX_SPEED_PER_SECOND);
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auto speed_y = clamp(distance_y * SPEED_FACTOR, -MAX_SPEED_PER_SECOND, MAX_SPEED_PER_SECOND);
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auto elapsed_seconds = SCROLL_INTERVAL_MS / 1000.0;
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m_fractional_delta += CSSPixelPoint {
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CSSPixels(speed_x * elapsed_seconds),
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CSSPixels(speed_y * elapsed_seconds),
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};
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auto scroll_x = m_fractional_delta.x().to_int();
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auto scroll_y = m_fractional_delta.y().to_int();
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m_fractional_delta -= CSSPixelPoint { scroll_x, scroll_y };
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paintable_box->scroll_by(scroll_x, scroll_y);
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}
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}
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